A numerical study for low motion FPSO with solid ballast tank

Abstract

Normally, it is widely accepted that conventional FPSOs are not suitable for hosting Top-Tensioned Risers (TTRs) or Steel Catenary Risers (SCRs) in most environments due to their high motion response compared to those of TLPs and SPARs. Recently, an innovative FPSO design has been introduced to solve this limitation of conventional FPSOs. In this paper, this novel FPSO design marketed under the name of LM-FPSO; Low Motion FPSO, is analyzed in terms of its motion characteristics. LM-FPSO is basically a combination of displacement type hull structure and a Solid Ballast Tank (SBT) located certain distance below the hull keel and attached to the hull structure by using a number of short tendons. This paper aims to evaluate the heave motion response of the LM-FPSO. In order to evaluate the advantages of the SBT to the heave response, a potential flow solver by using higher order boundary element method is applied in motion analysis of LM-FPSO, while CFD analysis approach is utilized for prediction of the damping ratios of the SBT and hull. In the meantime, hydrodynamic characteristics of heave damping on the SBT with different tendon's stiffness are compared. It is noted that validation of the numerical results will be carried out in the near future through model testing, which will be presented appropriately. Copyright ？ 2016 by the International Society of Offshore and Polar Engineers.